(1) Field of the Invention
This invention relates to an optical connector containing an optical plug, in which a spring cap is fitted on a plug housing.
(2) Description of the Related Art
An optical connector has been used when optical fibers (optical fiber cable) constructing multiple transmission circuits mounted in vehicles such as motorcars are connected to a transmitter, receiver or other cables.
The optical connector consists of an optical plug 1 shown in FIG. 7 and a receptacle (not shown in the figure) into which the optical plug 1 fits. The optical plug 1 consists of a pair of ferrule assemblies 2, a plug housing 3 and a spring cap 4, wherein the ferrule assemblies 2 are received in a pair of cavities 5 of the plug housing 3 and the spring cap 4 is fitted on the plug housing 3 from the rear thereof.
In the following, the construction of the optical plug 1 will be explained in detail.
Each ferrule assembly 2 consists of an optical fiber 6, a spring 7 and a ferrule 8, wherein the ferrule 8 is attached to an end of the optical fiber 6, around which the spring.7 is covered through in advance. A core 9 of the optical fiber 6 stick s out from a front end face of the ferrule 8 and one end of the spring 7 abuts on a rear end face of the ferrule 8.
The plug housing 3 is formed in rectangular box-shape, in which the cavities 5 are formed penetrating from the front to the rear of the plug housing 3. On a center of the upper surface of the plug housing 3, a locking arm 10 which is used when the plug housing 3 fits into the receptacle (not shown in the figure) is formed. At each rear end of the side surface of the plug housing 3, a pair of holding pieces 11 (only one of which shown in the figure), which holds an introduced optical fibers 6 in cooperation with a pair of holders 13 (explained later) of the spring cap 4, is formed.
The spring cap 4 is formed to be fitted on the rear of the plug housing 3, in which a pair of slits 12 for inserting the optical fibers 6 therein is formed on a pair of side walls and a part of rear wall of the spring cap 4. At the periphery of the slits 12 on the rear wall of the spring cap 4, a pair of the holders 13 (only one of which shown in the figure) having U-shape in cross-sectional view protrudes. A fitting part 14 of the spring cap 4 allows the spring cap 4 to fit on the plug housing 3. At a center of the upper wall of the spring cap 4, which faces the fitting part 14, a pair of protective walls 15 is formed to receive the locking arm 10. An opposite end of the spring 7 abuts on the rear wall of the spring cap 4.
As for the spring cap 4 of the above optical connector, since the spring cap 4 is simply fitted on the rear of the plug housing 3 by mean of the fitting part 14, disability in communication might take place under severe using conditions if things come to the worst.
That is, since the slits 12 having a width wide enough to insert at least the fibers 6 therein are formed over a wide range in the spring cap 4, when the optical connector is exposed at an elevated temperature for long period of time, the spring cap 4 might vary with time with a high probability, then an inconvenience such that the spring cap 4 opens widely in a direction shown by arrow P in FIG. 7 because of the slits 12 takes place.
When the spring cap 4 further varies with time and the spring cap 4 opens more widely, a holding power to hold the springs 7 deteriorates, resulting in not only increase in connecting loss between the optical plug 1 and the receptacle (not shown in the figure) and but also that the spring cap 4 might come off from the plug housing 3 and that disability in communication takes place if things come to the worst.
One measure to respond the problem mentioned above is to construct an optical plug 17 containing a spring cap 16 having no slit therein as shown in FIG. 8, said construction belonging to the conventional structure of the optical plug.
According to the above measure, the problem mentioned above can be solved, however, since the ferrule assemblies 19 must be formed after the spring cap 16 is connected to a pair of optical fibers 18 in advance, working efficiency becomes very low. Furthermore, since an inserting force between a pair of engaging parts 21 of the spring cap 16 and a pair of corresponding engaging projections 22 of the plug housing 20 becomes large, resulting in that the spring cap 16 becomes hard to be fitted on the plug housing 20.
Therefore, when the optical plug 17 having the structure mentioned above is employed, the problem different from that of the above optical plug 1 arises.
It is therefore an objective of the present invention to solve the above problems and to provide an optical connector, in which a spring cap easily fits on and hardly comes off from a plug housing.
In order to attain the above objective, the present invention is to provide an optical connector including an optical plug comprising: a ferrule assembly having a ferrule which is attached to an end of an optical fiber penetrated through a spring and can be abutted on one end of the spring; a plug housing for receiving the ferrule assembly; and a spring cap fitting on the plug housing by allowing an opposite end of the spring to abut thereon, wherein the plug housing includes a pair of guide rails formed on an upper surface of the plug housing and extended along an fitting direction of the spring cap with the plug housing and a pair of engaging projections each formed on right and left side surfaces of the plug housing, the spring cap includes a base facing to a bottom surface of the plug housing and a pair of side walls raised vertically from the base and each facing to said right or left side surface of the plug housing, a pair of said side walls each is divided along the fitting direction of the spring cap into portions for establishing a portion to bend and a portion to control aging, a pair of engaging parts each engaging with the respective engaging projection is formed on the portion to bend, grooves having an inverse U-shape cross-section are formed at the portion to control aging extending along the fitting direction of the spring cap with the plug housing by opening the base side of the spring cap for inserting the guide rail thereinto from one end thereof.
With the construction described above, since the engaging part of the spring cap engaging with the engaging projection of the plug housing is formed in the portion to bend, when the spring cap is fitted on the plug housing, an engagement of the engaging part with the engaging projection is completed after the side wall restores to its original state from its bent state.
The groove formed in the portion to control aging, into which the guide rail is inserted from one end of the groove, slides the guide rail therethrough until the engagement of the engaging part with the engaging projection is completed.
Since the groove is formed in inverse U-shape in cross-sectional view in the portion to control aging by opening the base side of the spring cap, when the spring cap is fitted on the plug housing, aging in a direction between the groove and the base of the spring cap can be restrained. In addition, because the groove has an inverse U-shape in cross-sectional view, aging in a direction between both side walls can be restrained.
Since the spring cap is constructed as described above, a portion for inserting the optical fiber is not required to be formed over a wide range in the spring cap like a slit in the conventional spring cap.
Consequently, as for the spring cap, the side wall in the portion to bend bends upon fitting of the spring cap with the plug housing and the groove in the portion to control aging inserts the guide rail therein so as to prevent the spring cap from aging.
A pair of the guide rails is disposed at the periphery of the upper surface of the plug housing so that each plane of the guide rail is the same with that of the respective right or left side surface of the plug housing.
With the construction described above, since the guide rail is disposed at the periphery of the upper surface of the plug housing, the corresponding groove is by no means situated at a position far from a plane of the side wall of the spring cap. That is, the distance from the side wall is kept short, thereby stiffness and strength of the groove become high.
An opposite end of the groove is in one body with a rear wall, on which said opposite end of the spring abuts, situating between a pair of said side walls of the spring cap.
With the construction described above, since the rear wall, on which the opposite end of the spring of the ferrule assembly abuts, supports the groove, thereby stiffness and strength of the groove become high.